Modelling, design and analysis of a water jetpack powered by an autonomous underwater vehicle (AUV) system.

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This dissertation describes the development and analysis of a water jetpack powered by an AUV system. The UKZN water jetpack has been in development since 2015 and has demonstrated the ability and potential for high performance flight characteristics from tests conducted during the first phase of its development. The objective of the current research is to develop a series of static and dynamic models such as to optimize the performance, efficiency and functionality of the water jetpack along with the development of an AUV concept to serve as a duel controlled power unit to the water jetpack. In particular, this dissertation details the development of an initial proposed water jetpack and AUV system computational model concept, together with static and dynamic modelling, mechanical and control system model development, as well as technical analysis of the water jetpack and AUV system for futuristic development and implementation.
A water jetpack propulsion system utilizes a feed hose which links the water jetpack to a separately tethered power unit, generally referred to as a personal water craft (PWC), which requires either secondary pilot control or tension-type tethering in the feed hose to enable the power unit to track the global positioning system (GPS) coordinates and match the dynamic state of the water jetpack. An AUV is an air independent propulsion (AIP) craft with the ability of GPS tracking, multi-degree of freedom control and simultaneously functioning as a PWC for the water jetpack system.
Research and analysis into the development of water jetpack’s, AUV’s, fluid dynamics, mechatronics and hydrogen AIP is presented in the study. From the research conducted, it is deduced that the aerodynamic stability and performance of a water jetpack is strongly dependent on the precise control of the mass flow rate, thrust vectoring, tracking and propulsion efficiency of the system. A series of non-transient models were developed and programmed as an optimization code on MATLAB to verify the geometric flow area range and performance of the water jetpack propulsion system under peak steady state conditions.
Development of the combined system control system consisted of modelling the open-loop first and second-order one-, two- and three-dimensional dynamic equations of the water jetpack and AUV on MATLAB Simulink. The open-loop system responses show there is a high degree of aerodynamic instability in the system due to a large overshoot and settling time. Proportional-integral-derivative (PID) controllers were implemented in each open-loop model to form closed-loop feedback control models of the water jetpack and AUV system such that a pilot can attain steady state aerodynamic stability and the AUV can track the GPS coordinates and dynamic state of the water jetpack. The system was modelled and simulated to reach a peak flight altitude of 10 m at which the system attains steady state control. The absolute peak condition for the water jetpack and AUV combined system is flight altitude of 10 m and flight velocity of 15 m/s. The development of the optimization code of the water jetpack propulsion system allowed for determining the system parameters used in the open and closed Simulink models. The development of the control system model and simulations conducted yielded a fully automated water jetpack and AUV system with optimized flight and aerodynamic performance. A computational model of the system was developed using SolidWorks and optimized as a function of mass, numerical and statistical performance. Thereafter, a series of detailed Computational Fluid Dynamics (CFD) and Finite Element Analyses (FEA) were performed to verify fluid flow optimization and structural integrity of the water jetpack propulsion system and AUV hull model under peak conditions that the system would be subjected to. The outcome of this study is the initial idea and theoretical analysis for a water jetpack and AUV system arising from fundamental theory, system modelling, system architecture, detailed analysis and an initial computational model for future development of the system.